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llvm-project/llvm/lib/Transforms/Instrumentation/RSProfiling.cpp

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//===- RSProfiling.cpp - Various profiling using random sampling ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// These passes implement a random sampling based profiling. Different methods
// of choosing when to sample are supported, as well as different types of
// profiling. This is done as two passes. The first is a sequence of profiling
// passes which insert profiling into the program, and remember what they
// inserted.
//
// The second stage duplicates all instructions in a function, ignoring the
// profiling code, then connects the two versions togeather at the entry and at
// backedges. At each connection point a choice is made as to whether to jump
// to the profiled code (take a sample) or execute the unprofiled code.
//
// It is highly recommended that after this pass one runs mem2reg and adce
// (instcombine load-vn gdce dse also are good to run afterwards)
//
// This design is intended to make the profiling passes independent of the RS
// framework, but any profiling pass that implements the RSProfiling interface
// is compatible with the rs framework (and thus can be sampled)
//
// TODO: obviously the block and function profiling are almost identical to the
// existing ones, so they can be unified (esp since these passes are valid
// without the rs framework).
// TODO: Fix choice code so that frequency is not hard coded
//
//===----------------------------------------------------------------------===//
#include "llvm/Pass.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Instructions.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Intrinsics.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Instrumentation.h"
#include "RSProfiling.h"
#include <set>
#include <map>
#include <queue>
using namespace llvm;
namespace {
enum RandomMeth {
GBV, GBVO, HOSTCC
};
}
static cl::opt<RandomMeth> RandomMethod("profile-randomness",
cl::desc("How to randomly choose to profile:"),
cl::values(
clEnumValN(GBV, "global", "global counter"),
clEnumValN(GBVO, "ra_global",
"register allocated global counter"),
clEnumValN(HOSTCC, "rdcc", "cycle counter"),
clEnumValEnd));
namespace {
/// NullProfilerRS - The basic profiler that does nothing. It is the default
/// profiler and thus terminates RSProfiler chains. It is useful for
/// measuring framework overhead
class VISIBILITY_HIDDEN NullProfilerRS : public RSProfilers {
public:
static char ID; // Pass identification, replacement for typeid
bool isProfiling(Value* v) {
return false;
}
bool runOnModule(Module &M) {
return false;
}
void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
}
static RegisterAnalysisGroup<RSProfilers> A("Profiling passes");
static RegisterPass<NullProfilerRS> NP("insert-null-profiling-rs",
"Measure profiling framework overhead");
static RegisterAnalysisGroup<RSProfilers, true> NPT(NP);
namespace {
/// Chooser - Something that chooses when to make a sample of the profiled code
class VISIBILITY_HIDDEN Chooser {
public:
/// ProcessChoicePoint - is called for each basic block inserted to choose
/// between normal and sample code
virtual void ProcessChoicePoint(BasicBlock*) = 0;
/// PrepFunction - is called once per function before other work is done.
/// This gives the opertunity to insert new allocas and such.
virtual void PrepFunction(Function*) = 0;
virtual ~Chooser() {}
};
//Things that implement sampling policies
//A global value that is read-mod-stored to choose when to sample.
//A sample is taken when the global counter hits 0
class VISIBILITY_HIDDEN GlobalRandomCounter : public Chooser {
GlobalVariable* Counter;
Value* ResetValue;
const IntegerType* T;
public:
GlobalRandomCounter(Module& M, const IntegerType* t, uint64_t resetval);
virtual ~GlobalRandomCounter();
virtual void PrepFunction(Function* F);
virtual void ProcessChoicePoint(BasicBlock* bb);
};
//Same is GRC, but allow register allocation of the global counter
class VISIBILITY_HIDDEN GlobalRandomCounterOpt : public Chooser {
GlobalVariable* Counter;
Value* ResetValue;
AllocaInst* AI;
const IntegerType* T;
public:
GlobalRandomCounterOpt(Module& M, const IntegerType* t, uint64_t resetval);
virtual ~GlobalRandomCounterOpt();
virtual void PrepFunction(Function* F);
virtual void ProcessChoicePoint(BasicBlock* bb);
};
//Use the cycle counter intrinsic as a source of pseudo randomness when
//deciding when to sample.
class VISIBILITY_HIDDEN CycleCounter : public Chooser {
uint64_t rm;
Constant *F;
public:
CycleCounter(Module& m, uint64_t resetmask);
virtual ~CycleCounter();
virtual void PrepFunction(Function* F);
virtual void ProcessChoicePoint(BasicBlock* bb);
};
/// ProfilerRS - Insert the random sampling framework
struct VISIBILITY_HIDDEN ProfilerRS : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
ProfilerRS() : FunctionPass(&ID) {}
std::map<Value*, Value*> TransCache;
std::set<BasicBlock*> ChoicePoints;
Chooser* c;
//Translate and duplicate values for the new profile free version of stuff
Value* Translate(Value* v);
//Duplicate an entire function (with out profiling)
void Duplicate(Function& F, RSProfilers& LI);
//Called once for each backedge, handle the insertion of choice points and
//the interconection of the two versions of the code
void ProcessBackEdge(BasicBlock* src, BasicBlock* dst, Function& F);
bool runOnFunction(Function& F);
bool doInitialization(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
};
}
static RegisterPass<ProfilerRS>
X("insert-rs-profiling-framework",
"Insert random sampling instrumentation framework");
char RSProfilers::ID = 0;
char NullProfilerRS::ID = 0;
char ProfilerRS::ID = 0;
//Local utilities
static void ReplacePhiPred(BasicBlock* btarget,
BasicBlock* bold, BasicBlock* bnew);
static void CollapsePhi(BasicBlock* btarget, BasicBlock* bsrc);
template<class T>
static void recBackEdge(BasicBlock* bb, T& BackEdges,
std::map<BasicBlock*, int>& color,
std::map<BasicBlock*, int>& depth,
std::map<BasicBlock*, int>& finish,
int& time);
//find the back edges and where they go to
template<class T>
static void getBackEdges(Function& F, T& BackEdges);
///////////////////////////////////////
// Methods of choosing when to profile
///////////////////////////////////////
GlobalRandomCounter::GlobalRandomCounter(Module& M, const IntegerType* t,
uint64_t resetval) : T(t) {
ConstantInt* Init = ConstantInt::get(T, resetval);
ResetValue = Init;
Counter = new GlobalVariable(M, T, false, GlobalValue::InternalLinkage,
Init, "RandomSteeringCounter");
}
GlobalRandomCounter::~GlobalRandomCounter() {}
void GlobalRandomCounter::PrepFunction(Function* F) {}
void GlobalRandomCounter::ProcessChoicePoint(BasicBlock* bb) {
BranchInst* t = cast<BranchInst>(bb->getTerminator());
//decrement counter
LoadInst* l = new LoadInst(Counter, "counter", t);
ICmpInst* s = new ICmpInst(t, ICmpInst::ICMP_EQ, l,
ConstantInt::get(T, 0),
"countercc");
Value* nv = BinaryOperator::CreateSub(l, ConstantInt::get(T, 1),
"counternew", t);
new StoreInst(nv, Counter, t);
t->setCondition(s);
//reset counter
BasicBlock* oldnext = t->getSuccessor(0);
BasicBlock* resetblock = BasicBlock::Create("reset", oldnext->getParent(),
oldnext);
TerminatorInst* t2 = BranchInst::Create(oldnext, resetblock);
t->setSuccessor(0, resetblock);
new StoreInst(ResetValue, Counter, t2);
ReplacePhiPred(oldnext, bb, resetblock);
}
GlobalRandomCounterOpt::GlobalRandomCounterOpt(Module& M, const IntegerType* t,
uint64_t resetval)
: AI(0), T(t) {
ConstantInt* Init = ConstantInt::get(T, resetval);
ResetValue = Init;
Counter = new GlobalVariable(M, T, false, GlobalValue::InternalLinkage,
Init, "RandomSteeringCounter");
}
GlobalRandomCounterOpt::~GlobalRandomCounterOpt() {}
void GlobalRandomCounterOpt::PrepFunction(Function* F) {
//make a local temporary to cache the global
BasicBlock& bb = F->getEntryBlock();
BasicBlock::iterator InsertPt = bb.begin();
AI = new AllocaInst(T, 0, "localcounter", InsertPt);
LoadInst* l = new LoadInst(Counter, "counterload", InsertPt);
new StoreInst(l, AI, InsertPt);
//modify all functions and return values to restore the local variable to/from
//the global variable
for(Function::iterator fib = F->begin(), fie = F->end();
fib != fie; ++fib)
for(BasicBlock::iterator bib = fib->begin(), bie = fib->end();
bib != bie; ++bib)
if (isa<CallInst>(bib)) {
LoadInst* l = new LoadInst(AI, "counter", bib);
new StoreInst(l, Counter, bib);
l = new LoadInst(Counter, "counter", ++bib);
new StoreInst(l, AI, bib--);
} else if (isa<InvokeInst>(bib)) {
LoadInst* l = new LoadInst(AI, "counter", bib);
new StoreInst(l, Counter, bib);
BasicBlock* bb = cast<InvokeInst>(bib)->getNormalDest();
BasicBlock::iterator i = bb->getFirstNonPHI();
l = new LoadInst(Counter, "counter", i);
bb = cast<InvokeInst>(bib)->getUnwindDest();
i = bb->getFirstNonPHI();
l = new LoadInst(Counter, "counter", i);
new StoreInst(l, AI, i);
} else if (isa<UnwindInst>(&*bib) || isa<ReturnInst>(&*bib)) {
LoadInst* l = new LoadInst(AI, "counter", bib);
new StoreInst(l, Counter, bib);
}
}
void GlobalRandomCounterOpt::ProcessChoicePoint(BasicBlock* bb) {
BranchInst* t = cast<BranchInst>(bb->getTerminator());
//decrement counter
LoadInst* l = new LoadInst(AI, "counter", t);
ICmpInst* s = new ICmpInst(t, ICmpInst::ICMP_EQ, l,
ConstantInt::get(T, 0),
"countercc");
Value* nv = BinaryOperator::CreateSub(l, ConstantInt::get(T, 1),
"counternew", t);
new StoreInst(nv, AI, t);
t->setCondition(s);
//reset counter
BasicBlock* oldnext = t->getSuccessor(0);
BasicBlock* resetblock = BasicBlock::Create("reset", oldnext->getParent(),
oldnext);
TerminatorInst* t2 = BranchInst::Create(oldnext, resetblock);
t->setSuccessor(0, resetblock);
new StoreInst(ResetValue, AI, t2);
ReplacePhiPred(oldnext, bb, resetblock);
}
CycleCounter::CycleCounter(Module& m, uint64_t resetmask) : rm(resetmask) {
F = Intrinsic::getDeclaration(&m, Intrinsic::readcyclecounter);
}
CycleCounter::~CycleCounter() {}
void CycleCounter::PrepFunction(Function* F) {}
void CycleCounter::ProcessChoicePoint(BasicBlock* bb) {
BranchInst* t = cast<BranchInst>(bb->getTerminator());
CallInst* c = CallInst::Create(F, "rdcc", t);
BinaryOperator* b =
BinaryOperator::CreateAnd(c, ConstantInt::get(Type::Int64Ty, rm),
"mrdcc", t);
ICmpInst *s = new ICmpInst(t, ICmpInst::ICMP_EQ, b,
ConstantInt::get(Type::Int64Ty, 0),
"mrdccc");
t->setCondition(s);
}
///////////////////////////////////////
// Profiling:
///////////////////////////////////////
bool RSProfilers_std::isProfiling(Value* v) {
if (profcode.find(v) != profcode.end())
return true;
//else
RSProfilers& LI = getAnalysis<RSProfilers>();
return LI.isProfiling(v);
}
void RSProfilers_std::IncrementCounterInBlock(BasicBlock *BB, unsigned CounterNum,
GlobalValue *CounterArray) {
// Insert the increment after any alloca or PHI instructions...
BasicBlock::iterator InsertPos = BB->getFirstNonPHI();
while (isa<AllocaInst>(InsertPos))
++InsertPos;
// Create the getelementptr constant expression
std::vector<Constant*> Indices(2);
Indices[0] = BB->getContext().getNullValue(Type::Int32Ty);
Indices[1] = ConstantInt::get(Type::Int32Ty, CounterNum);
Constant *ElementPtr =
BB->getContext().getConstantExprGetElementPtr(CounterArray,
&Indices[0], 2);
// Load, increment and store the value back.
Value *OldVal = new LoadInst(ElementPtr, "OldCounter", InsertPos);
profcode.insert(OldVal);
Value *NewVal = BinaryOperator::CreateAdd(OldVal,
ConstantInt::get(Type::Int32Ty, 1),
"NewCounter", InsertPos);
profcode.insert(NewVal);
profcode.insert(new StoreInst(NewVal, ElementPtr, InsertPos));
}
void RSProfilers_std::getAnalysisUsage(AnalysisUsage &AU) const {
//grab any outstanding profiler, or get the null one
AU.addRequired<RSProfilers>();
}
///////////////////////////////////////
// RS Framework
///////////////////////////////////////
Value* ProfilerRS::Translate(Value* v) {
if(TransCache[v])
return TransCache[v];
if (BasicBlock* bb = dyn_cast<BasicBlock>(v)) {
if (bb == &bb->getParent()->getEntryBlock())
TransCache[bb] = bb; //don't translate entry block
else
TransCache[bb] = BasicBlock::Create("dup_" + bb->getName(),
bb->getParent(), NULL);
return TransCache[bb];
} else if (Instruction* i = dyn_cast<Instruction>(v)) {
//we have already translated this
//do not translate entry block allocas
if(&i->getParent()->getParent()->getEntryBlock() == i->getParent()) {
TransCache[i] = i;
return i;
} else {
//translate this
Instruction* i2 = i->clone(v->getContext());
if (i->hasName())
i2->setName("dup_" + i->getName());
TransCache[i] = i2;
//NumNewInst++;
for (unsigned x = 0; x < i2->getNumOperands(); ++x)
i2->setOperand(x, Translate(i2->getOperand(x)));
return i2;
}
} else if (isa<Function>(v) || isa<Constant>(v) || isa<Argument>(v)) {
TransCache[v] = v;
return v;
}
llvm_unreachable("Value not handled");
return 0;
}
void ProfilerRS::Duplicate(Function& F, RSProfilers& LI)
{
//perform a breadth first search, building up a duplicate of the code
std::queue<BasicBlock*> worklist;
std::set<BasicBlock*> seen;
//This loop ensures proper BB order, to help performance
for (Function::iterator fib = F.begin(), fie = F.end(); fib != fie; ++fib)
worklist.push(fib);
while (!worklist.empty()) {
Translate(worklist.front());
worklist.pop();
}
//remember than reg2mem created a new entry block we don't want to duplicate
worklist.push(F.getEntryBlock().getTerminator()->getSuccessor(0));
seen.insert(&F.getEntryBlock());
while (!worklist.empty()) {
BasicBlock* bb = worklist.front();
worklist.pop();
if(seen.find(bb) == seen.end()) {
BasicBlock* bbtarget = cast<BasicBlock>(Translate(bb));
BasicBlock::InstListType& instlist = bbtarget->getInstList();
for (BasicBlock::iterator iib = bb->begin(), iie = bb->end();
iib != iie; ++iib) {
//NumOldInst++;
if (!LI.isProfiling(&*iib)) {
Instruction* i = cast<Instruction>(Translate(iib));
instlist.insert(bbtarget->end(), i);
}
}
//updated search state;
seen.insert(bb);
TerminatorInst* ti = bb->getTerminator();
for (unsigned x = 0; x < ti->getNumSuccessors(); ++x) {
BasicBlock* bbs = ti->getSuccessor(x);
if (seen.find(bbs) == seen.end()) {
worklist.push(bbs);
}
}
}
}
}
void ProfilerRS::ProcessBackEdge(BasicBlock* src, BasicBlock* dst, Function& F) {
//given a backedge from B -> A, and translations A' and B',
//a: insert C and C'
//b: add branches in C to A and A' and in C' to A and A'
//c: mod terminators@B, replace A with C
//d: mod terminators@B', replace A' with C'
//e: mod phis@A for pred B to be pred C
// if multiple entries, simplify to one
//f: mod phis@A' for pred B' to be pred C'
// if multiple entries, simplify to one
//g: for all phis@A with pred C using x
// add in edge from C' using x'
// add in edge from C using x in A'
//a:
Function::iterator BBN = src; ++BBN;
BasicBlock* bbC = BasicBlock::Create("choice", &F, BBN);
//ChoicePoints.insert(bbC);
BBN = cast<BasicBlock>(Translate(src));
BasicBlock* bbCp = BasicBlock::Create("choice", &F, ++BBN);
ChoicePoints.insert(bbCp);
//b:
BranchInst::Create(cast<BasicBlock>(Translate(dst)), bbC);
BranchInst::Create(dst, cast<BasicBlock>(Translate(dst)),
ConstantInt::get(Type::Int1Ty, true), bbCp);
//c:
{
TerminatorInst* iB = src->getTerminator();
for (unsigned x = 0; x < iB->getNumSuccessors(); ++x)
if (iB->getSuccessor(x) == dst)
iB->setSuccessor(x, bbC);
}
//d:
{
TerminatorInst* iBp = cast<TerminatorInst>(Translate(src->getTerminator()));
for (unsigned x = 0; x < iBp->getNumSuccessors(); ++x)
if (iBp->getSuccessor(x) == cast<BasicBlock>(Translate(dst)))
iBp->setSuccessor(x, bbCp);
}
//e:
ReplacePhiPred(dst, src, bbC);
//src could be a switch, in which case we are replacing several edges with one
//thus collapse those edges int the Phi
CollapsePhi(dst, bbC);
//f:
ReplacePhiPred(cast<BasicBlock>(Translate(dst)),
cast<BasicBlock>(Translate(src)),bbCp);
CollapsePhi(cast<BasicBlock>(Translate(dst)), bbCp);
//g:
for(BasicBlock::iterator ib = dst->begin(), ie = dst->end(); ib != ie;
++ib)
if (PHINode* phi = dyn_cast<PHINode>(&*ib)) {
for(unsigned x = 0; x < phi->getNumIncomingValues(); ++x)
if(bbC == phi->getIncomingBlock(x)) {
phi->addIncoming(Translate(phi->getIncomingValue(x)), bbCp);
cast<PHINode>(Translate(phi))->addIncoming(phi->getIncomingValue(x),
bbC);
}
phi->removeIncomingValue(bbC);
}
}
bool ProfilerRS::runOnFunction(Function& F) {
if (!F.isDeclaration()) {
std::set<std::pair<BasicBlock*, BasicBlock*> > BackEdges;
RSProfilers& LI = getAnalysis<RSProfilers>();
getBackEdges(F, BackEdges);
Duplicate(F, LI);
//assume that stuff worked. now connect the duplicated basic blocks
//with the originals in such a way as to preserve ssa. yuk!
for (std::set<std::pair<BasicBlock*, BasicBlock*> >::iterator
ib = BackEdges.begin(), ie = BackEdges.end(); ib != ie; ++ib)
ProcessBackEdge(ib->first, ib->second, F);
//oh, and add the edge from the reg2mem created entry node to the
//duplicated second node
TerminatorInst* T = F.getEntryBlock().getTerminator();
ReplaceInstWithInst(T, BranchInst::Create(T->getSuccessor(0),
cast<BasicBlock>(
Translate(T->getSuccessor(0))),
ConstantInt::get(Type::Int1Ty, true)));
//do whatever is needed now that the function is duplicated
c->PrepFunction(&F);
//add entry node to choice points
ChoicePoints.insert(&F.getEntryBlock());
for (std::set<BasicBlock*>::iterator
ii = ChoicePoints.begin(), ie = ChoicePoints.end(); ii != ie; ++ii)
c->ProcessChoicePoint(*ii);
ChoicePoints.clear();
TransCache.clear();
return true;
}
return false;
}
bool ProfilerRS::doInitialization(Module &M) {
switch (RandomMethod) {
case GBV:
c = new GlobalRandomCounter(M, Type::Int32Ty, (1 << 14) - 1);
break;
case GBVO:
c = new GlobalRandomCounterOpt(M, Type::Int32Ty, (1 << 14) - 1);
break;
case HOSTCC:
c = new CycleCounter(M, (1 << 14) - 1);
break;
};
return true;
}
void ProfilerRS::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<RSProfilers>();
AU.addRequiredID(DemoteRegisterToMemoryID);
}
///////////////////////////////////////
// Utilities:
///////////////////////////////////////
static void ReplacePhiPred(BasicBlock* btarget,
BasicBlock* bold, BasicBlock* bnew) {
for(BasicBlock::iterator ib = btarget->begin(), ie = btarget->end();
ib != ie; ++ib)
if (PHINode* phi = dyn_cast<PHINode>(&*ib)) {
for(unsigned x = 0; x < phi->getNumIncomingValues(); ++x)
if(bold == phi->getIncomingBlock(x))
phi->setIncomingBlock(x, bnew);
}
}
static void CollapsePhi(BasicBlock* btarget, BasicBlock* bsrc) {
for(BasicBlock::iterator ib = btarget->begin(), ie = btarget->end();
ib != ie; ++ib)
if (PHINode* phi = dyn_cast<PHINode>(&*ib)) {
std::map<BasicBlock*, Value*> counter;
for(unsigned i = 0; i < phi->getNumIncomingValues(); ) {
if (counter[phi->getIncomingBlock(i)]) {
assert(phi->getIncomingValue(i) == counter[phi->getIncomingBlock(i)]);
phi->removeIncomingValue(i, false);
} else {
counter[phi->getIncomingBlock(i)] = phi->getIncomingValue(i);
++i;
}
}
}
}
template<class T>
static void recBackEdge(BasicBlock* bb, T& BackEdges,
std::map<BasicBlock*, int>& color,
std::map<BasicBlock*, int>& depth,
std::map<BasicBlock*, int>& finish,
int& time)
{
color[bb] = 1;
++time;
depth[bb] = time;
TerminatorInst* t= bb->getTerminator();
for(unsigned i = 0; i < t->getNumSuccessors(); ++i) {
BasicBlock* bbnew = t->getSuccessor(i);
if (color[bbnew] == 0)
recBackEdge(bbnew, BackEdges, color, depth, finish, time);
else if (color[bbnew] == 1) {
BackEdges.insert(std::make_pair(bb, bbnew));
//NumBackEdges++;
}
}
color[bb] = 2;
++time;
finish[bb] = time;
}
//find the back edges and where they go to
template<class T>
static void getBackEdges(Function& F, T& BackEdges) {
std::map<BasicBlock*, int> color;
std::map<BasicBlock*, int> depth;
std::map<BasicBlock*, int> finish;
int time = 0;
recBackEdge(&F.getEntryBlock(), BackEdges, color, depth, finish, time);
DEBUG(errs() << F.getName() << " " << BackEdges.size() << "\n");
}
//Creation functions
ModulePass* llvm::createNullProfilerRSPass() {
return new NullProfilerRS();
}
FunctionPass* llvm::createRSProfilingPass() {
return new ProfilerRS();
}
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